Multiorder diffractive (MOD) lenses are useful for bringing a plurality of spectral components of different wavelengths to a common focus, and are described in U.S. Pat. No. 5,589,982, which is herein incorporated by reference. The MOD lens has a structure of multiple annular zones having step heights defining zone boundaries, which diffract light of each of the wavelengths in a different diffractive order to a common focus. Such a MOD lens has not been applied to bifocal optics for vision correction.
Conventional bifocal optics for spectacles are provided by lenses having lower and upper regions of different refractive power for near and distance (far) vision correction. For contact lenses and IOLs, multifocal refractive optics have been proposed with the anterior and/or posterior surfaces of a lens (or IOL optic) shaped to provide a central zone, annular near zones, and annular distance zones of different refractive powers. Such bifocal refractive lenses do not utilize diffractive structures for near or distance vision correction. Examples of multifocal refractive lenses for contacts and IOLs are shown in U.S. Pat. Nos. 6,231,603, 5,805,260, 5,798,817, 5,715,031, 5,682,223, and U.S. Publication No. US2003/0014107 A1. Other multifocal refractive lenses have other zones, such as pie, hyperbolic, or pin-wheel shaped near and distance zones, as shown in U.S. Pat. Nos. 5,512,220 and 5,507,979, or spiral shaped zones, as shown in U.S. Pat. Nos. 5,517,260 and 5,408,281. Moreover, refractive lenses are generally thicker than diffractive lens for equivalent optical power, and thickness reduction is often desirable in ophthalmic applications, such as contact lenses and IOLs.
Non-MOD diffractive optics for multifocal ophthalmic applications exist having a lens with a surface providing a diffractive structure of concentric zones of different step heights for near and far vision correction, such as described, for example, in U.S. Pat. No. 5,699,142. Another multifocal diffractive lens, described in U.S. Pat. No. 5,748,282, has a similar diffractive structure with a region having a reduced step height to reduce intensity of light from such region. A further multifocal diffractive lens is described in U.S. Pat. No. 5,116,111 also has a similar non-MOD diffractive structure in which the base power of lens may be provided by refraction of the lens. The diffractive lenses of U.S. Pat. Nos. 5,699,142, 5,748,282, and 5,116,111 lack the ability of the MOD lens to focus light of different wavelengths to a common focus for either near or far vision correction by their reliance on non-MOD structures. Other non-MOD optics may be segmented to provide multiple regions, but are not multifocal. For example, U.S. Pat. No. 5,071,207 describes a non-MOD diffractive lens having pie-shaped segments in which all the segments of the lens are limited to focusing light to a common focus. Thus, prior approaches to multifocal or bifocal optics have utilized refractive surfaces or non-MOD structures.